U.S. patent application number 12/890182 was filed with the patent office on 2011-09-29 for ue-rs sequence initialization for wireless communication systems.
This patent application is currently assigned to QUALCOMM INCORPORATED. Invention is credited to Naga Bhushan, Wanshi Chen, Amir Farajidana, Alexei Yurievitch Gorokhov, Aamod Dinkar Khandekar, Tao Luo, Juan Montojo.
Application Number | 20110237267 12/890182 |
Document ID | / |
Family ID | 43431879 |
Filed Date | 2011-09-29 |
United States Patent
Application |
20110237267 |
Kind Code |
A1 |
Chen; Wanshi ; et
al. |
September 29, 2011 |
UE-RS SEQUENCE INITIALIZATION FOR WIRELESS COMMUNICATION
SYSTEMS
Abstract
Pseudo-random sequences of a plurality of user equipment
specific reference signals (UE-RSs) for use by a plurality of user
equipments (UEs) are initialized, the initialization of each
pseudo-random sequence associated with each UE-RS being independent
of a specific UE identifier and independent of a resource bandwidth
assigned to a specific UE. Pseudo-random sequences of the UE-RSs
are generated. At least one of the pseudo-random sequences is
mapped to a portion of common resources for at least one UE among
the plurality of UEs.
Inventors: |
Chen; Wanshi; (San Diego,
CA) ; Montojo; Juan; (San Diego, CA) ; Luo;
Tao; (San Diego, CA) ; Gorokhov; Alexei
Yurievitch; (San Diego, CA) ; Khandekar; Aamod
Dinkar; (San Diego, CA) ; Bhushan; Naga; (San
Diego, CA) ; Farajidana; Amir; (Sunnyvale,
CA) |
Assignee: |
QUALCOMM INCORPORATED
San Diego
CA
|
Family ID: |
43431879 |
Appl. No.: |
12/890182 |
Filed: |
September 24, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61247491 |
Sep 30, 2009 |
|
|
|
61248830 |
Oct 5, 2009 |
|
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Current U.S.
Class: |
455/450 |
Current CPC
Class: |
H04J 11/003 20130101;
H04J 13/10 20130101; H04L 5/0051 20130101; H04J 11/005 20130101;
H04L 27/2613 20130101; H04L 5/0023 20130101; H04J 13/16
20130101 |
Class at
Publication: |
455/450 |
International
Class: |
H04W 72/04 20090101
H04W072/04 |
Claims
1. A method of data communication in a wireless communication
system, comprising: initializing pseudo-random sequences of a
plurality of user equipment specific reference signals (UE-RSs) for
use by a plurality of user equipments (UEs), the initialization of
each pseudo-random sequence associated with each UE-RS being
independent of a specific UE identifier and independent of a
resource bandwidth assigned to a specific UE; generating
pseudo-random sequences of the UE-RSs; and mapping at least one of
the pseudo-random sequences to a portion of common resources for at
least one UE among the plurality of UEs.
2. The method of claim 1, wherein in the initializing step,
c.sub.init is an initial value of a pseudo-random sequence
generator associated with the each UE-RS and is a function defined
by c.sub.init=f(N.sub.ID.sup.cell,.left brkt-bot.n.sub.s/2.right
brkt-bot.), wherein N.sub.ID.sup.cell is a cell ID and n.sub.s is a
slot number.
3. The method of claim 1, wherein the initialization is based at
least in part on a maximum bandwidth configuration of the wireless
communication system.
4. The method of claim 1, wherein the pseudo-random sequences are
defined by r ( m ) = 1 2 ( 1 - 2 c ( 2 m ) ) + j 1 2 ( 1 - 2 c ( 2
m + 1 ) ) , m = 0 , 1 , , 12 N RB [ DL , max ] - 1 , ##EQU00003##
wherein c is a pseudo-random sequence generator, and
N.sub.RB.sup.[DL,max] denotes a maximum downlink bandwidth
configuration of the wireless communication system.
5. The method of claim 4, wherein N.sub.RB.sup.[DL,max] is 110
resource blocks (RBs).
6. The method of claim 1, wherein the initialization is based at
least in part on an identifier indicative of a resource block
(RB).
7. The method of claim 6, wherein in the initializing step,
c.sub.init is an initial value of a pseudo-random sequence
generator associated with the each UE-RS and is a function defined
by c.sub.init=f(N.sub.ID.sup.cell,.left brkt-bot.n.sub.s/2.right
brkt-bot., RB.sub.ID), wherein: N.sub.ID.sup.cell is a cell ID,
n.sub.s is a slot number, and RB.sub.ID is a resource block (RB)
identifier.
8. The method of claim 1, wherein the initialization is based at
least in part on an index indicative of an antenna port.
9. The method of claim 8, wherein in the initialization step,
c.sub.init is an initial value of a pseudo-random sequence
generator associated with the each UE-RS and is a function defined
by c.sub.init=f(N.sub.ID.sup.cell,.left brkt-bot.n.sub.s/2.right
brkt-bot., AntPortIdx), wherein: N.sub.ID.sup.cell is a cell ID,
n.sub.s is a slot number, and AntPortIdx is an antenna port
index.
10. The method of claim 1, wherein the initialization is based at
least in part on a group ID, the group ID corresponding to a UE
group to which at least one UE is assigned.
11. The method of claim 10, wherein in the initializing step,
c.sub.init is an initial value of a pseudo-random sequence
generator associated with the each UE-RS and is a function defined
by c.sub.init=f(N.sub.ID.sup.cell,.left brkt-bot.n.sub.s/2.right
brkt-bot., n_groupID), wherein: N.sub.ID.sup.cell is a cell ID,
n.sub.s is a slot number, and n_groupID is a group ID.
12. The method of claim 10, further comprising assigning the group
ID in a semi-static manner.
13. The method of claim 10, further comprising assigning the group
ID in a dynamic manner.
14. The method of claim 11, wherein there are two groups, a first
one of the two groups having n_groupID=0, and a second one of the
two groups having n_groupID=1.
15. The method of claim 10, wherein the at least one UE is assigned
to the UE group based on one of a UE location, a UE dominant
channel direction and a total number of current UEs assigned to the
UE group.
16. A method of data communication in a wireless communication
system, comprising: receiving at least one pseudo-random sequence
of a user equipment specific reference signal (UE-RS), the at least
one pseudo-random sequence having been initialized independent of a
specific UE identifier and independent of a resource bandwidth
assigned to a specific UE; receiving data on a downlink bandwidth
resource; and using the UE-RS to decode data received on the
downlink bandwidth resource.
17. The method of claim 16, wherein the at least one pseudo-random
sequence is based at least in part on a maximum bandwidth
configuration of the wireless communication system.
18. The method of claim 16, wherein the at least one pseudo-random
sequence has been initialized based at least in part on an
identifier indicative of a resource block (RB).
19. The method of claim 16, wherein the at least one pseudo-random
sequence has been initialized based at least in part on an index
indicative of an antenna port.
20. The method of claim 16, wherein the pseudo-random sequence has
been initialized based at least in part on a group ID, the group ID
corresponding to a UE group to which at least one UE is
assigned.
21. An apparatus in a wireless communication network, comprising:
at least one processor configured to: initialize pseudo-random
sequences of a plurality of user equipment specific reference
signals (UE-RSs) for use by a plurality of user equipments (UEs),
the initialization of each pseudo-random sequence associated with
each UE-RS being independent of a specific UE identifier and
independent of a resource bandwidth assigned to a specific UE,
generate pseudo-random sequences of the UE-RSs, and map at least
one of the pseudo-random sequences to a portion of common resources
for at least one UE among the plurality of UEs.
22. The apparatus of claim 21, wherein in the initialization of
each pseudo-random sequence, c.sub.init is an initial value of a
pseudo-random sequence generator associated with the each UE-RS and
is a function defined by c.sub.init=f(N.sub.ID.sup.cell,.left
brkt-bot.n.sub.s/2.right brkt-bot.), wherein N.sub.ID.sup.cell is a
cell ID and n.sub.s is a slot number.
23. The apparatus of claim 21, wherein the initialization is based
at least in part on a maximum bandwidth configuration of the
wireless communication system.
24. The apparatus of claim 21, wherein the pseudo-random sequences
are defined by r ( m ) = 1 2 ( 1 - 2 c ( 2 m ) ) + j 1 2 ( 1 - 2 c
( 2 m + 1 ) ) , m = 0 , 1 , , 12 N RB [ DL , max ] - 1 ,
##EQU00004## wherein c is a pseudo-random sequence generator, and
N.sub.RB.sup.[DL,max] denotes a maximum downlink bandwidth
configuration of the wireless communication system.
25. The apparatus of claim 21, wherein the initialization is based
at least in part on an identifier indicative of a resource block
(RB).
26. The apparatus of claim 21, wherein the initialization is based
at least in part on an index indicative of an antenna port.
27. The apparatus of claim 21, wherein the initialization is based
at least in part on a group ID, the group ID corresponding to a UE
group to which at least one UE is assigned.
28. The apparatus of claim 27, wherein the at least one processor
is further configured to assign the group ID in one of a
semi-static manner and a dynamic manner.
29. An apparatus in a wireless communication system, comprising: at
least one processor configured to: receive at least one
pseudo-random sequence of a user equipment specific reference
signal (UE-RS), the at least one pseudo-random sequence having been
initialized independent of a specific UE identifier and independent
of a resource bandwidth assigned to the UE, receive data on a
downlink bandwidth resource, and use the UE-RS to decode data
received on the downlink bandwidth resource.
30. The apparatus of claim 29, wherein the at least one
pseudo-random sequence is based at least in part on a maximum
bandwidth configuration of the wireless communication system.
31. The apparatus of claim 29, wherein the at least one
pseudo-random sequence has been initialized based at least in part
on an identifier indicative of a resource block (RB).
32. The apparatus of claim 29, wherein the at least one
pseudo-random sequence has been initialized based at least in part
on an index indicative of an antenna port.
33. The UE of claim 29, wherein the pseudo-random sequence has been
initialized based at least in part on a group ID, the group ID
corresponding to a UE group to which at least one UE is
assigned.
34. An apparatus in a wireless communication network, comprising:
means for initializing pseudo-random sequences of a plurality of
user equipment specific reference signals (UE-RSs) for use by a
plurality of user equipments (UEs), the initialization of each
pseudo-random sequence associated with each UE-RS being independent
of a specific UE identifier and independent of a resource bandwidth
assigned to a specific UE; means for generating pseudo-random
sequences of the UE-RSs; and means for mapping at least one of the
pseudo-random sequences to a portion of common resources for at
least one UE among the plurality of UEs.
35. The apparatus of claim 34, wherein in the initialization of
each pseudo-random sequence, c.sub.init is an initial value of a
pseudo-random sequence generator associated with the each UE-RS and
is a function defined by c.sub.init=f(N.sub.ID.sup.cell,.left
brkt-bot.n.sub.s/2.right brkt-bot.), wherein N.sub.ID.sup.cell is a
cell ID and n.sub.s is a slot number.
36. The apparatus of claim 34, wherein the initialization is based
at least in part on a maximum bandwidth configuration of the
wireless communication system.
37. The apparatus of claim 34, wherein the pseudo-random sequences
are defined by r ( m ) = 1 2 ( 1 - 2 c ( 2 m ) ) + j 1 2 ( 1 - 2 c
( 2 m + 1 ) ) , m = 0 , 1 , , 12 N RB [ DL , max ] - 1 ,
##EQU00005## wherein c is a pseudo-random sequence generator, and
N.sub.RB.sup.[DL,max] denotes a maximum downlink bandwidth
configuration of the wireless communication system.
38. The apparatus of claim 34, wherein the initialization of based
at least in part on an identifier indicative of a resource block
(RB).
39. The apparatus of claim 34, wherein the initialization is based
at least in part on an index indicative of an antenna port.
40. The apparatus of claim 34, wherein the initialization is based
at least in part on a group ID, the group ID corresponding to a UE
group to which at least one UE is assigned.
41. The apparatus of claim 40, further comprising means for
assigning the group ID in one of a semi-static manner and a dynamic
manner.
42. An apparatus in a wireless communication system, comprising:
means for receiving at least one pseudo-random sequence of a user
equipment specific reference signal (UE-RS), the at least one
pseudo-random sequence having been initialized independent of a
specific UE identifier and independent of a resource bandwidth
assigned to the UE; means for receiving data on a downlink
bandwidth resource; and means for using the UE-RS to decode data
received on the downlink bandwidth resource.
43. The apparatus of claim 42, wherein the at least one
pseudo-random sequence is based at least in part on a maximum
bandwidth configuration of the wireless communication system.
44. The apparatus of claim 42, wherein the at least one
pseudo-random sequence has been initialized based at least in part
on an identifier indicative of a resource block (RB).
45. The apparatus of claim 42, wherein the at least one
pseudo-random sequence has been initialized based on an index
indicative of an antenna port.
46. The apparatus of claim 42, wherein the at least one
pseudo-random sequence has been initialized based at least in part
on a group ID, the group ID corresponding to a UE group to which at
least one UE is assigned.
47. A computer-readable medium having computer readable
instructions stored thereon for execution by at least one processor
to perform a method comprising: initializing pseudo-random
sequences of a plurality of user equipment specific reference
signals (UE-RSs) for use by a plurality of user equipments (UEs),
the initialization of each pseudo-random sequence associated with
each UE-RS being independent of a specific UE identifier and
independent of a resource bandwidth assigned to a specific UE;
generating pseudo-random sequences of the UE-RSs; and mapping at
least one of the pseudo-random sequences to a portion of common
resources for at least one UE among the plurality of UEs.
48. The computer-readable medium of claim 47, wherein the
pseudo-random sequences are based at least in part on a maximum
bandwidth configuration of the wireless communication system.
49. The computer-readable medium of claim 47, wherein the
initialization is based at least in part on a group ID, the group
ID corresponding to a UE group to which at least one UE is
assigned.
50. A computer-readable medium having computer readable
instructions stored thereon for execution by at least one processor
to perform a method comprising: receiving at least one
pseudo-random sequence of a user equipment specific reference
signal (UE-RS), the at least one pseudo-random sequence having been
initialized independent of a specific UE identifier and independent
of a resource bandwidth assigned to the UE; receiving data on a
downlink bandwidth resource; and using the UE-RS to decode data
received on the downlink bandwidth resource.
51. The computer-readable medium of claim 50, wherein the at least
one pseudo-random sequence is based at least in part on a maximum
bandwidth configuration of the wireless communication system.
52. The computer-readable medium of claim 50, wherein the at least
one pseudo-random sequence has been initialized based at least in
part on a group ID, the group ID corresponding to a UE group to
which at least one UE is assigned.
Description
CROSS-REFERENCE
[0001] The present application claims the benefit of U.S.
Provisional Patent Application Ser. No. 61/247,491, entitled "UE-RS
SEQUENCE INITIALIZATION FOR REL-9 AND BEYOND," filed on Sep. 30,
2009 and U.S. Provisional Patent Application Ser. No. 61/248,830,
entitled "UE-RS SEQUENCE INITIALIZATION FOR REL-9 AND BEYOND,"
filed on Oct. 5, 2009, each of which is hereby incorporated by
reference in its entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present disclosure relates generally to wireless
communication, and more specifically for reference signal (RS)
sequence initialization for wireless communication systems.
[0004] 2. Relevant Background
[0005] Wireless communication systems are widely deployed to
provide various types of communication content such as voice, data,
and so on. These systems may be multiple-access systems capable of
supporting communication with multiple users by sharing the
available system resources (e.g., bandwidth and transmit power).
Examples of such multiple-access systems include code division
multiple access (CDMA) systems, time division multiple access
(TDMA) systems, frequency division multiple access (FDMA) systems,
3GPP Long Term Evolution (LTE) systems, and orthogonal frequency
division multiple access (OFDMA) systems.
[0006] Generally, a wireless multiple-access communication system
can simultaneously support communication for multiple wireless
terminals. Each terminal communicates with one or more base
stations via transmissions on the forward and reverse links. The
forward link (or downlink, DL) refers to the communication link
from the base stations to the terminals, and the reverse link (or
uplink, UL) refers to the communication link from the terminals to
the base stations. This communication link may be established via a
single-in-single-out, multiple-in-signal-out or a
multiple-in-multiple-out (MIMO) system.
[0007] A MIMO system employs multiple (N.sub.T) transmit antennas
and multiple (N.sub.R) receive antennas for data transmission. A
MIMO channel formed by the N.sub.T transmit and N.sub.R receive
antennas may be decomposed into N.sub.S independent channels, which
are also referred to as spatial channels, where
N.sub.S.ltoreq.min{N.sub.T, N.sub.R}. Each of the N.sub.S
independent channels corresponds to a dimension. The MIMO system
can provide improved performance (e.g., higher throughput and/or
greater reliability) if the additional dimensionalities created by
the multiple transmit and receive antennas are utilized.
[0008] In addition, multi-user MIMO (MU-MIMO) systems are provided
that allow an access point (or other wireless device) to
simultaneously transmit to multiple UEs (or other wireless devices)
using MIMO over a single frequency band. In this regard, access
points can transmit UE specific reference signals (RS) to the UEs
for demodulating data transmitted simultaneously in one or more
signals in the frequency band. In LTE Release 8 (Rel-8) for
single-layer beamforming, UE RS sequences are defined in terms of
bandwidth of one or more resource blocks of a corresponding
downlink transmission. In addition, pseudo-random sequences for the
UE RS are generated according to a UE-specific identifier.
SUMMARY
[0009] The following presents a simplified summary in order to
provide a basic understanding of some aspects of the disclosed
aspects. This summary is not an extensive overview and is intended
to neither identify key or critical elements nor delineate the
scope of such aspects. Its purpose is to present some concepts of
the described features in a simplified form as a prelude to the
more detailed description that is presented later.
[0010] In accordance with one or more aspects and corresponding
disclosure thereof, various aspects are described in connection
with assigning and initializing sequences of UE-RSs in MU-MIMO
configurations.
[0011] In certain aspects, a method of data communication in a
wireless communication system is provided. The method can comprise
initializing pseudo-random sequences of a plurality of user
equipment specific reference signals (UE-RSs) for use by a
plurality of user equipments (UEs), the initialization of each
pseudo-random sequence associated with each UE-RS being independent
of a specific UE identifier and independent of a resource bandwidth
assigned to a specific UE. The method can further comprise
generating pseudo-random sequences of the UE-RSs. The method can
further comprise mapping at least one of the pseudo-random
sequences to a portion of common resources for at least one UE
among the plurality of UEs.
[0012] In certain aspects, a method of data communication in a
wireless communication system is provided. The method can comprise
receiving at least one pseudo-random sequence of a user equipment
specific reference signal (UE-RS), the at least one pseudo-random
sequence having been initialized independent of a specific UE
identifier and independent of a resource bandwidth assigned to a
specific UE. The method can further comprise receiving data on a
downlink bandwidth resource. The method can further comprise using
the UE-RS to decode data received on the downlink bandwidth
resource.
[0013] In certain aspects, an apparatus in a wireless communication
network is provided. The apparatus can comprise at least one
processor configured to initialize pseudo-random sequences of a
plurality of user equipment specific reference signals (UE-RSs) for
use by a plurality of user equipments (UEs), the initialization of
each pseudo-random sequence associated with each UE-RS being
independent of a specific UE identifier and independent of a
resource bandwidth assigned to a specific UE; generate
pseudo-random sequences of the UE-RSs; and map at least one of the
pseudo-random sequences to a portion of common resources for at
least one UE among the plurality of UEs. The apparatus can further
comprise a memory coupled to the at least one processor.
[0014] In certain aspects, an apparatus in a wireless communication
system is provided. The apparatus can comprise at least one
processor configured to receive at least one pseudo-random sequence
of a user equipment specific reference signal (UE-RS), the at least
one pseudo-random sequence having been initialized independent of a
specific UE identifier and independent of a resource bandwidth
assigned to the UE; receive data on a downlink bandwidth resource;
and use the UE-RS to decode data received on the downlink bandwidth
resource. The apparatus can further comprise a memory coupled to
the at least one processor.
[0015] In certain aspects, an apparatus in a wireless communication
network is provided. The apparatus can comprise means for
initializing pseudo-random sequences of a plurality of user
equipment specific reference signals (UE-RSs) for use by a
plurality of user equipments (UEs), the initialization of each
pseudo-random sequence associated with each UE-RS being independent
of a specific UE identifier and independent of a resource bandwidth
assigned to a specific UE. The apparatus can further comprise means
for generating pseudo-random sequences of the UE-RSs. The apparatus
can further comprise means for mapping at least one of the
pseudo-random sequences to a portion of common resources for at
least one UE among the plurality of UEs.
[0016] In certain aspects, an apparatus in a wireless communication
system is provided. The apparatus can comprise means for receiving
at least one pseudo-random sequence of a user equipment specific
reference signal (UE-RS), the at least one pseudo-random sequence
having been initialized independent of a specific UE identifier and
independent of a resource bandwidth assigned to the UE. The
apparatus can further comprise means for receiving data on a
downlink bandwidth resource. The apparatus can further comprise
means for using the UE-RS to decode data received on the downlink
bandwidth resource.
[0017] In certain aspects, a computer-readable medium having
computer readable instructions stored thereon for execution by at
least one processor to perform a method is provided. The method can
comprise initializing pseudo-random sequences of a plurality of
user equipment specific reference signals (UE-RSs) for use by a
plurality of user equipments (UEs), the initialization of each
pseudo-random sequence associated with each UE-RS being independent
of a specific UE identifier and independent of a resource bandwidth
assigned to a specific UE. The method can further comprise
generating pseudo-random sequences of the UE-RSs. The method can
further comprise mapping at least one of the pseudo-random
sequences to a portion of common resources for at least one UE
among the plurality of UEs.
[0018] In certain aspects, a computer-readable medium having
computer readable instructions stored thereon for execution by at
least one processor to perform a method is provided. The method can
comprise receiving at least one pseudo-random sequence of a user
equipment specific reference signal (UE-RS), the at least one
pseudo-random sequence having been initialized independent of a
specific UE identifier and independent of a resource bandwidth
assigned to the UE. The method can further comprise receiving data
on a downlink bandwidth resource. The method can further comprise
using the UE-RS to decode data received on the downlink bandwidth
resource.
[0019] To the accomplishment of the foregoing and related ends, one
or more aspects comprise the features hereinafter fully described
and particularly pointed out in the claims. The following
description and the annexed drawings set forth in detail certain
illustrative aspects and are indicative of but a few of the various
ways in which the principles of the aspects may be employed. Other
advantages and novel features will become apparent from the
following detailed description when considered in conjunction with
the drawings and the disclosed aspects are intended to include all
such aspects and their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The features, nature, and advantages of the present
disclosure will become more apparent from the detailed description
set forth below when taken in conjunction with the drawings in
which like reference characters identify correspondingly throughout
and wherein:
[0021] FIG. 1 is a diagram illustrating a multiple access wireless
communication system.
[0022] FIG. 2 is a block diagram illustrating a communication
system.
[0023] FIG. 3 is a block diagram illustrating an exemplary system
that facilitates defining, initializing and mapping reference
signals (RSs) in MU-MIMO configurations.
[0024] FIG. 4 is a block diagram illustrating PUSCH assignments for
various user equipments (UEs) in MU-MIMO configurations.
[0025] FIG. 5 is a flowchart illustrating an exemplary process for
assigning and initializing sequences of UE-RSs in MU-MIMO
configurations from a viewpoint of an access point.
[0026] FIG. 6 is a flowchart illustrating an exemplary process for
receiving and using sequences of UE-RSs in MU-MIMO configurations
from a viewpoint of a user equipment (UE).
[0027] FIG. 7 is a block diagram illustrating an exemplary system
that facilitates defining, initializing and mapping RSs in MU-MIMO
configurations.
[0028] FIG. 8 is a flowchart illustrating an exemplary process for
assigning and initializing sequences of UE-RSs in MU-MIMO
configurations from a viewpoint of an access point.
[0029] FIG. 9 is a flowchart illustrating an exemplary process for
receiving and using sequences of UE-RSs in MU-MIMO configurations
from a viewpoint of a user equipment (UE).
DETAILED DESCRIPTION
[0030] Various aspects are now described with reference to the
drawings. In the following description, for purposes of
explanation, numerous specific details are set forth in order to
provide a thorough understanding of one or more aspects. It may be
evident, however, that the various aspects may be practiced without
these specific details. In other instances, well-known structures
and devices are shown in block diagram form in order to facilitate
describing these aspects.
[0031] The techniques described herein may be used for various
wireless communication networks such as Code Division Multiple
Access (CDMA) networks, Time Division Multiple Access (TDMA)
networks, Frequency Division Multiple Access (FDMA) networks,
Orthogonal FDMA (OFDMA) networks, Single-Carrier FDMA (SC-FDMA)
networks, etc. The terms "networks" and "systems" are often used
interchangeably. A CDMA network may implement a radio technology
such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc.
UTRA includes Wideband-CDMA (W-CDMA) and Low Chip Rate (LCR).
cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network
may implement a radio technology such as Global System for Mobile
Communications (GSM). An OFDMA network may implement a radio
technology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16,
IEEE 802.20, Flash-OFDM.RTM., etc. UTRA, E-UTRA, and GSM are part
of Universal Mobile Telecommunication System (UMTS). Long Term
Evolution (LTE) is an upcoming release of UMTS that uses E-UTRA.
UTRA, E-UTRA, GSM, UMTS and LTE are described in documents from an
organization named "3rd Generation Partnership Project" (3GPP).
cdma2000 is described in documents from an organization named "3rd
Generation Partnership Project 2" (3GPP2). These various radio
technologies and standards are known in the art. For clarity,
certain illustrative aspects of the techniques are described below
for LTE, and LTE terminology is used in much of the description
below.
[0032] Single carrier frequency division multiple access (SC-FDMA),
which utilizes single carrier modulation and frequency domain
equalization is a technique. SC-FDMA has similar performance and
essentially the same overall complexity as those of OFDMA system.
SC-FDMA signal has lower peak-to-average power ratio (PAPR) because
of its inherent single carrier structure. SC-FDMA has drawn great
attention, especially in the uplink communications where lower PAPR
greatly benefits the mobile terminal in terms of transmit power
efficiency. It is currently a working assumption for uplink
multiple access scheme in 3GPP Long Term Evolution (LTE), or
Evolved UTRA.
[0033] Referring to FIG. 1, a multiple access wireless
communication system according to one embodiment is illustrated. An
access point 100 (AP) includes multiple antenna groups, one
including 104 and 106, another including 108 and 110, and an
additional including 112 and 114. In FIG. 1, only two antennas are
shown for each antenna group, however, more or fewer antennas may
be utilized for each antenna group. Access terminal 116 (AT) is in
communication with antennas 112 and 114, where antennas 112 and 114
transmit information to access terminal 116 over forward link 120
and receive information from access terminal 116 over reverse link
118. Access terminal 122 is in communication with antennas 106 and
108, where antennas 106 and 108 transmit information to access
terminal 122 over forward link 126 and receive information from
access terminal 122 over reverse link 124. In a FDD system,
communication links 118, 120, 124 and 126 may use different
frequency for communication. For example, forward link 120 may use
a different frequency then that used by reverse link 118.
[0034] Each group of antennas and/or the area in which they are
designed to communicate is often referred to as a sector of the
access point. In the embodiment, antenna groups each are designed
to communicate to access terminals in a sector, of the areas
covered by access point 100.
[0035] In communication over forward links 120 and 126, the
transmitting antennas of access point 100 utilize beamforming in
order to improve the signal-to-noise ratio of forward links for the
different access terminals 116 and 122. Also, an access point using
beamforming to transmit to access terminals scattered randomly
through its coverage causes less interference to access terminals
in neighboring cells than an access point transmitting through a
single antenna to all its access terminals.
[0036] An access point may be a fixed station used for
communicating with the terminals and may also be referred to as an
access point, a Node B, evolved Node B (eNB), or some other
terminology. An access terminal may also be called an access
terminal, user equipment (UE), a wireless communication device,
terminal, access terminal or some other terminology. Moreover, an
access point be a macrocell access point, femtocell access point,
picocell access point, and/or the like.
[0037] Additionally, as described, access point 100 can communicate
with access terminals 116 and 122 using MIMO, single-user MIMO
(SU-MIMO), multi-user MIMO (MU-MIMO), and/or the like. In this
regard, access point 100 can transmit reference signals (RSs) to
the access terminals 116 and 122 that can be used for demodulating
subsequent signals sent from the access point 100. In an example,
the RSs can be UE specific. In one example, RSs for access
terminals 116 and 122 (and/or additional access terminals
communicating with access point 100) can be CDM, FDM, and/or a
combination of CDM and FDM to facilitate diversity.
[0038] FIG. 2 is a block diagram of an embodiment of a transmitter
system 210 (can be an access point or access terminal) and a
receiver system 250 (can be an access terminal or access point) in
a MIMO system 200. At the transmitter system 210, traffic data for
a number of data streams is provided from a data source 212 to a
transmit (TX) data processor 214.
[0039] In an embodiment, each data stream is transmitted over a
respective transmit antenna. TX data processor 214 formats, codes,
and interleaves the traffic data for each data stream based on a
particular coding scheme selected for that data stream to provide
coded data.
[0040] The coded data for each data stream may be multiplexed with
pilot data using OFDM techniques. The pilot data is typically a
known data pattern that is processed in a known manner and may be
used at the receiver system to estimate the channel response. The
multiplexed pilot and coded data for each data stream is then
modulated (i.e., symbol mapped) based on a particular modulation
scheme (e.g., BPSK, QSPK, M-PSK, or M-QAM) selected for that data
stream to provide modulation symbols. The data rate, coding, and
modulation for each data stream may be determined by instructions
performed by processor 230.
[0041] The modulation symbols for all data streams are then
provided to a TX MIMO processor 220, which may further process the
modulation symbols (e.g., for OFDM). TX MIMO processor 220 then
provides N.sub.T modulation symbol streams to N.sub.T transmitters
(TMTR) 222a through 222t. In certain embodiments, TX MIMO processor
220 applies beamforming weights to the symbols of the data streams
and to the antenna from which the symbol is being transmitted.
[0042] Each transmitter 222 receives and processes a respective
symbol stream to provide one or more analog signals, and further
conditions (e.g., amplifies, filters, and upconverts) the analog
signals to provide a modulated signal suitable for transmission
over the MIMO channel. N.sub.T modulated signals from transmitters
222a through 222t are then transmitted from N.sub.T antennas 224a
through 224t, respectively.
[0043] At receiver system 250, the transmitted modulated signals
are received by N.sub.R antennas 252a through 252r and the received
signal from each antenna 252 is provided to a respective receiver
(RCVR) 254a through 254r. Each receiver 254 conditions (e.g.,
filters, amplifies, and downconverts) a respective received signal,
digitizes the conditioned signal to provide samples, and further
processes the samples to provide a corresponding "received" symbol
stream.
[0044] An RX data processor 260 then receives and processes the
N.sub.R received symbol streams from N.sub.R receivers 254 based on
a particular receiver processing technique to provide N.sub.T
"detected" symbol streams. The RX data processor 260 then
demodulates, deinterleaves, and decodes each detected symbol stream
to recover the traffic data for the data stream. The processing by
RX data processor 260 is complementary to that performed by TX MIMO
processor 220 and TX data processor 214 at transmitter system
210.
[0045] A processor 270 periodically determines which pre-coding
matrix to use (discussed below). Processor 270 formulates a reverse
link message comprising a matrix index portion and a rank value
portion.
[0046] The reverse link message may comprise various types of
information regarding the communication link and/or the received
data stream. The reverse link message is then processed by a TX
data processor 238, which also receives traffic data for a number
of data streams from a data source 236, modulated by a modulator
280, conditioned by transmitters 254a through 254r, and transmitted
back to transmitter system 210.
[0047] At transmitter system 210, the modulated signals from
receiver system 250 are received by antennas 224, conditioned by
receivers 222, demodulated by a demodulator 240, and processed by a
RX data processor 242 to extract the reserve link message
transmitted by the receiver system 250. Processor 230 then
determines which pre-coding matrix to use for determining the
beamforming weights then processes the extracted message.
[0048] In an aspect, logical channels are classified into Control
Channels and Traffic Channels. Logical Control Channels comprises
Broadcast Control Channel (BCCH) which is DL channel for
broadcasting system control information. Paging Control Channel
(PCCH) which is DL channel that transfers paging information.
Multicast Control Channel (MCCH) which is Point-to-multipoint DL
channel used for transmitting Multimedia Broadcast and Multicast
Service (MBMS) scheduling and control information for one or
several MBMS Traffic Channels (MTCHs). Generally, after
establishing a Radio Resource Control (RRC) connection this channel
is only used by UEs that receive MBMS (Note: old MCCH+MSCH).
Dedicated Control Channel (DCCH) is a point-to-point bi-directional
channel that transmits dedicated control information and is used by
UEs having an RRC connection. In aspect, Logical Traffic Channels
comprises a Dedicated Traffic Channel (DTCH) which is a
point-to-point bi-directional channel, dedicated to one UE, for the
transfer of user information. Also, a Multicast Traffic Channel
(MTCH) is a point-to-multipoint DL channel for transmitting traffic
data.
[0049] In an aspect, Transport Channels are classified into
downlink (DL) and uplink (UL). DL Transport Channels comprises a
Broadcast Channel (BCH), Downlink Shared Data Channel (DL-SDCH) and
a Paging Channel (PCH), the PCH for support of UE power saving (DRX
cycle is indicated by the network to the UE), broadcasted over
entire cell and mapped to PHY resources which can be used for other
control/traffic channels. The UL Transport Channels comprises a
Random Access Channel (RACH), a Request Channel (REQCH), a Uplink
Shared Data Channel (UL-SDCH) and plurality of PHY channels. The
PHY channels comprises a set of DL channels and UL channels.
[0050] The DL PHY channels comprise: Physical Downlink Shared
Channel (PDSCH), Physical Broadcast Channel (PBSH), Physical
Multicast Channel (PMCH), Physical Downlink Control Channel
(PDCCH), Physical Hybrid Automatic Repeat Request Indicator Channel
(PHICH), and Physical Control Format Indicator Channel
(PCFICH).
[0051] The UL PHY Channels comprise: Physical Random Access Channel
(PRACH), Physical Uplink Shared Channel (PUSCH), and Physical
Uplink Control Channel (PUCCH).
[0052] In an aspect, a channel structure is provided that preserves
low PAR (at any given time, the channel is contiguous or uniformly
spaced in frequency) properties of a single carrier waveform.
[0053] For the purposes of the present document, the following
abbreviations apply:
[0054] ACK Acknowledgement
[0055] AM Acknowledged Mode
[0056] AMD Acknowledged Mode Data
[0057] ARQ Automatic Repeat Request
[0058] BCCH Broadcast Control CHannel
[0059] BCH Broadcast CHannel
[0060] C- Control-
[0061] CCE Control Channel Element
[0062] CCCH Common Control CHannel
[0063] CCH Control CHannel
[0064] CCTrCH Coded Composite Transport Channel
[0065] CDM Code Division Multiplexing
[0066] CP Cyclic Prefix
[0067] CQI Channel Quality Indicator
[0068] CRC Cyclic Redundancy Check
[0069] CRS Common Reference Signal
[0070] CTCH Common Traffic CHannel
[0071] DCCH Dedicated Control CHannel
[0072] DCH Dedicated CHannel
[0073] DCI Downlink Control Information
[0074] DL DownLink
[0075] DRS Dedicated Reference Signal
[0076] DSCH Downlink Shared CHannel
[0077] DTCH Dedicated Traffic CHannel
[0078] E-CID Enhanced Cell IDentification
[0079] FACH Forward link Access CHannel
[0080] FDD Frequency Division Duplex
[0081] FSTD Frequency Switched Transmit Diversity
[0082] HARQ Hybrid Automatic Repeat/reQuest
[0083] L1 Layer 1 (physical layer)
[0084] L2 Layer 2 (data link layer)
[0085] L3 Layer 3 (network layer)
[0086] LI Length Indicator
[0087] LLR Log-Likelihood Ratio
[0088] LSB Least Significant Bit
[0089] MAC Medium Access Control
[0090] MBMS Multimedia Broadcast Multicast Service
[0091] MCCH MBMS point-to-multipoint Control CHannel
[0092] MRW Move Receiving Window
[0093] MSB Most Significant Bit
[0094] MSCH MBMS point-to-multipoint Scheduling CHannel
[0095] MTCH MBMS point-to-multipoint Traffic CHannel
[0096] NACK Non-Acknowledgement
[0097] PCCH Paging Control CHannel
[0098] PCH Paging CHannel
[0099] PDCCH Physical Downlink Control CHannel
[0100] PDU Protocol Data Unit
[0101] PHY PHYsical layer
[0102] PhyCH Physical CHannels
[0103] PMI Precoding Matrix Indicator
[0104] PRACH Physical Random Access CHannel
[0105] PUCCH Physical Uplink Control CHannel
[0106] RACH Random Access CHannel
[0107] RB Resource Block
[0108] RLC Radio Link Control
[0109] RRC Radio Resource Control
[0110] RE Resource Element
[0111] RS Reference Signal
[0112] RTT Round Trip Time
[0113] Rx Receive
[0114] SAP Service Access Point
[0115] SDU Service Data Unit
[0116] SFBC Space Frequency Block Code
[0117] SHCCH SHared channel Control CHannel
[0118] SN Sequence Number
[0119] SUFI SUper FIeld
[0120] TA Timing Advance
[0121] TCH Traffic CHannel
[0122] TDD Time Division Duplex
[0123] TFI Transport Format Indicator
[0124] TM Transparent Mode
[0125] TMD Transparent Mode Data
[0126] TTI Transmission Time Interval
[0127] Tx Transmit
[0128] U- User-
[0129] UE User Equipment
[0130] UL UpLink
[0131] UM Unacknowledged Mode
[0132] UMD Unacknowledged Mode Data
[0133] UMTS Universal Mobile Telecommunications System
[0134] UTRA UMTS Terrestrial Radio Access
[0135] UTRAN UMTS Terrestrial Radio Access Network
[0136] MBSFN multicast broadcast single frequency network
[0137] MCE MBMS coordinating entity
[0138] MCH multicast channel
[0139] DL-SCH downlink shared channel
[0140] MSCH MBMS control channel
[0141] PDCCH physical downlink control channel
[0142] PDSCH physical downlink shared channel
[0143] FIG. 3 illustrates an exemplary system 300 that facilitates
generating UE-RSs and related resource mappings in an MU-MIMO
configuration. System 300 includes an access point 302 that can be
a base station, femtocell access point, picocell access point,
relay node, mobile base station, mobile device operating in a
peer-to-peer communications mode, and/or the like, for example,
that provides wireless device 304 with access to a wireless
network. Wireless device 304 can be a user equipment (UE) such as a
mobile device, portion thereof, or substantially any device that
can access a wireless network.
[0144] Access point 302 can include a UE-RS sequence defining
component 306 that develops a plurality of reference signals that
can be used by one or more UEs to decode data over shared
resources, a UE-RS sequence initializing component 308 that creates
a pseudo-random sequence of the reference signals for the one or
more UEs, a UE-RS mapping component 310 that maps a UE to a given
pseudo-random sequence of UE-RSs, and an RS information signaling
component 312 that communicates the UE-RS mapping information to a
corresponding UE. Wireless device 304 can include an RS information
receiving component 314 that obtains one or more parameters related
to RS transmissions from an access point and an RS decoding
component 316 that decodes one or more RSs based at least in part
on the parameters.
[0145] According to an example, as described, RSs in an MU-MIMO
configuration can be CDM, FDM, and/or a combination thereof. For
example, where RSs are CDM, access point 302 can multiplex RSs
according to pseduo-random sequences selected for one or more
wireless devices. In an example, UE-RS sequence defining component
306 can generate a plurality of UE-RSs that can be utilized to
decode data sent over shared resources to one or more UEs. In
MU-MIMO configurations, it is to be appreciated that devices having
shared bandwidth assignments and/or location assignments may not be
completely aligned. Thus, UE-RS sequence defining component 306 can
generate the plurality of UE-RSs based on an entire bandwidth of a
related cell instead of based on PDSCH bandwidth (as in LTE release
8). In another aspect (e.g., to support multi-cell MU-MIMO), UE-RS
sequence defining component 306 can generate the UE-RSs in a
bandwidth agnostic manner, such as according to a largest downlink
bandwidth configuration in terms of resource block (RBs).
[0146] Once the UE-RSs are defined, UE-RS sequence initializing
component 308 can generate pseudo-random sequences of the UE-RS for
assigning to UEs to decode shared resources. In MU-MIMO
configurations, it can be desirable that antenna ports for wireless
devices paired to use the same PDSCH resources remain orthogonal.
To this end, UE-RS sequence initializing component 308 can
initialize the UE-RS sequences based at least in part on a cell
identifier (as opposed to a UE identifier in LTE release 8). This
can ensure orthogonality since the antenna ports use the common
metric. In this regard, for example, other common metrics can be
utilized, such as resource block identifier, antenna port index,
and/or the like, that can be known for both antenna ports. The
UE-RS mapping component 310 can assign the pseudo-random sequences
of UE-RS and shared resources to one or more wireless devices using
a pre-determined mapping scheme that maintains the orthogonality
(e.g., sequentially from one end of the band, starting from the
center of the band, etc.).
[0147] In FIG. 3, RS information signaling component 312 can signal
pseudo-random sequences of RS, related resources, and/or related
parameters corresponding to the wireless device 304. At wireless
device 304, RS information receiving component 314 can obtain the
received pseudo-random sequences of RS, related shared resources,
and/or parameters from the access point 302. RS decoding component
316 can decode RSs specific to wireless device 304 from access
point 302 over the shared resources using the pseudo-random
sequences, for example.
[0148] In some communication systems, UE-specific reference signal
(UE-RS) is specified to support single-layer beamforming. For
example, in DL transmission mode 7 of LTE Rel-8, the UE-RS sequence
r (m) is defined by:
r ( m ) = 1 2 ( 1 - 2 c ( 2 m ) ) + j 1 2 ( 1 - 2 c ( 2 m + 1 ) ) ,
m = 0 , 1 , , 12 N RB PDSCH - 1 ( 1 ) ##EQU00001##
where N.sub.RB.sup.PDSCH denotes the bandwidth in resource blocks
of the corresponding PDSCH transmission. The pseudo-random sequence
c(i) can be pre-defined. The pseudo-random sequence generator can
be initialized with:
c.sub.init=(.left brkt-bot.n.sub.s/2.right
brkt-bot.+1)(2N.sub.ID.sup.cell+1)2.sup.16+n.sub.RNTI (2)
at the start of each subframe where n.sub.RNTI is defined, and can
be a UE-specific ID.
[0149] In other communication systems, dual-stream beamforming
relying on two UE-RS antenna ports is supported. For example, in
LTE Rel-9, the following can be true: [0150] 1) The two antenna
ports are CDM-ed. [0151] 2) Dynamic rank adaptation is supported:
that is, a UE may be indicated either rank 1 or rank 2 DL
transmissions using layer 2 signaling (PDCCH). In case of rank 1
transmission, the UE is explicitly indicated which antenna port
should be used. [0152] 3) MU-MIMO is supported: that is, two UEs
may be paired using the same PDSCH resources. Each UE is indicated
the antenna port in use, but is not indicated whether it is in the
MU- or SU-MIMO transmission.
[0153] For MU-MIMO operation, it is advantageous that the two UE-RS
antenna ports for the paired UEs remain orthogonal after resource
mapping using the pseudo-random sequence and the assigned PDSCH
resources. However, as can be seen from equation (1) above, if the
sequence is initialized based on a UE specific ID, the sequences
generated for the paired UEs are no longer the same. As a result,
the orthogonality may not be maintained. In addition, one UE does
not know the pseudo-random sequence used by the other paired UE, as
the UE-IDs may not be mutually known between the paired UEs. Such
non-orthogonality and unknown information about the other random
sequence can cause significant interference on UE-RS.
[0154] Another issue is that when the random sequence is generated
dependent on the assigned PDSCH bandwidth (N.sub.RB.sup.PDSCH) and
mapped to the specific locations of the assigned PDSCH resources,
e.g., in (1). It is possible that UEs paired in MU-MIMO
transmissions may not be completely aligned, both in terms of the
assigned bandwidth and the assigned location, as illustrated in
FIG. 4. Turning to FIG. 4, shown is a first PDSCH 401 which is
assigned to a first UE and a second PDSCH 402 which is assigned to
a second UE that is paired with the first UE. It is clear that the
PDSCH bandwidths associated with the first and second PDSCHs 401,
402 are not aligned. In such a case, the pseudo-random sequences
for the paired UEs may not be orthogonal.
[0155] In view of the aforementioned issues, various UE-RS sequence
initialization schemes are employed, in which the initialization of
each pseudo-random (PR) sequence associated with each UE-RS is
independent of a specific UE identifier and independent of a
resource bandwidth assigned to a specific UE.
[0156] In one aspect, the UE-RS sequence initialization can be made
independent of a UE identifier in a number of different ways. In
certain embodiments, this can be achieved by simply removing the UE
identifier from the initialization. That is,
c.sub.init=(.left brkt-bot.n.sub.s/2.right
brkt-bot.+1)(2N.sub.ID.sup.cell+1)2.sup.16
The initialization is hence independent from UE specific IDs.
Generally speaking, one can have:
c.sub.init=f(N.sub.ID.sup.cell,.left brkt-bot.n.sub.s/2.right
brkt-bot.) (3)
The sequence is still cell-dependent and subframe-dependent.
Consequently, inter-cell interference randomization can still be
realized.
[0157] In some embodiments, the UE-RS sequence initialization can
be made independent of a specific UE identifier by making the
initialization as a function of a resource block identifier
(RB.sub.ID) and/or an antenna port index (AntPortIdx), expressed,
respectively, as:
c.sub.init=f(N.sub.ID.sup.cell,.left brkt-bot.n.sub.s/2.right
brkt-bot.,RB.sub.ID), and
c.sub.init=f(N.sub.ID.sup.cell,.left brkt-bot.n.sub.s/2.right
brkt-bot.,AntPortIdx)
Although orthogonality may not be maintained for some of the cases,
at least the sequence is known to the UEs paired in the MU-MIMO
transmissions. The RB.sub.ID can be generated either sequentially,
or following a specific sequence-to-resource mapping approach
(e.g., numbering starting from the middle and increase
upwards/downwards, similar to that of the common reference signal
(CRS) case).
[0158] In some embodiments, the UE-RS sequence initialization can
be a function of a cyclic prefix (CP) type (i.e., normal or
extended cyclic prefix). For example, the function can be expressed
as:
c init = f ( N ID cell , n s / 2 , N CP ) , where N cp = { 1 for
normal CP 0 for extended CP ##EQU00002##
[0159] In certain embodiments, different combinations of the above
dependencies may be employed. For example, the UE-RS sequence
initialization can be a function of 1) RB.sub.ID and AntPortIdx, 2)
RB.sub.ID and N.sub.CP, 3) AntPortIdx and N.sub.CP, or 4) RB.sub.ID
and AntPortIdx and N.sub.CP, etc.
[0160] In another aspect, the UE-RS random sequence generation can
be done such that the paired UEs still have orthogonal UE-RS
sequences, regardless of PDSCH resource allocations. This can be
achieved, for example, by making the UE-RS sequence generation
independent of a resource bandwidth assigned to a specific UE. This
way, dependency on resource bandwidth is removed, thereby
mitigating the need for related UEs to be aligned when receiving
UE-RS sequences and related resource assignments. In certain
embodiments, the UE-RS sequence generation is based on a maximum
possible bandwidth of a given cell, and mapped to the DL resources
in some pre-determined manner (e.g., sequentially from one end of
the band, or starting from the center of the band, etc.). In other
words, m=0, 1, . . . , 12N.sub.RB.sup.DL-1, where m is defined in
equation (1) above, and N.sub.RB.sup.DL denotes a DL bandwidth of a
specific cell in the wireless communication system.
[0161] In light of the possible support of multi-cell MU-MIMO, and
the fact that the common reference signal (CRS) is generated in a
bandwidth agnostic manner in LTE Rel-8, the UE-RS sequence can be
bandwidth-agnostic as well. That is, m=0, 1, . . . ,
12N.sub.RB.sup.[DL,max]-1, where N.sub.RB.sup.[DL, max] (may also
be referred to as N.sub.RB.sup.[max, DL]) is a maximum DL bandwidth
configuration in terms of number of RBs, e.g., 110 RBs. The mapping
of the generated UE-RS sequence to the UE-RS resources can be the
same as CRS (e.g., starting from the center, and mapping
downwards/upwards such that the mapping from the generated sequence
to the band is bandwidth-agnostic). To be more specific, the mapped
symbol a.sub.k,l.sup.(p) (where k is freq index; l is symbol index;
and p is antenna port index) can be similar to:
a.sub.k,l.sup.(p)=r.sub.l,n.sub.s (m'), where
m'=m+N.sub.RB.sup.max,DL-N.sub.RB.sup.DL, and k has a step size of
6 resource elements (vs. 12 resource elements or the RB size).
Thus, m' ranges from N.sub.RB.sup.[max,DL]-N.sub.RB.sup.DL to
N.sub.RB.sup.[max,DL]+N.sub.RB.sup.DL-1. Note that UE-RS can be
mapped on a per RB basis, instead of per 6 RBs as in the CRS
case.
[0162] FIG. 5 is a flowchart illustrating an exemplary process 500
for assigning and initializing sequences of UE-RSs in MU-MIMO
configurations from a viewpoint of an access point (e.g., eNB). The
process 500 begins at start state 501 and proceeds to operation 510
in which pseudo-random (PR) sequences of UE-RSs for use by a
plurality of UEs are initialized, where the initialization of each
PR sequence associated with each UE-RS is independent of a specific
UE identifier and/or independent of a resource bandwidth assigned
to a specific UE.
[0163] As described above, the first independence relating to the
UE-RS PR sequence initialization can be achieved by removing the UE
identifier from the initialization such as the one defined by
equation (3) above; and/or by making the initialization a function
of non-UE specific parameter such as RB.sub.ID, AntPortIdx,
RB.sub.ID, N.sub.CP, or any combinations thereof. The second
independence relating to the resource bandwidth can be achieved by
initializing a plurality of UE-RSs based at least in part on a
bandwidth of a specific cell that includes the plurality of UE-RSs.
As described above, this removes dependency on resource bandwidth
associated with the particular UE, which mitigates the need for
related UEs to be aligned when receiving UE-RS sequences and
related resource assignments.
[0164] The process 500 proceeds to operation 520 in which UE-RS PR
sequences are generated using a procedure defined by equation (1),
for example. The PR sequences can be generated using common (non-UE
specific) identifiers, such as a cell identifier
(N.sub.ID.sup.cell), resource block identifier (RB.sub.ID), etc.,
so cell antennas can retain orthogonality of sequence assignment
for devices having similar assigned resources.
[0165] The process 500 proceeds to operation 530 in which at least
one of the UE-RS PR sequences thus generated is mapped to a portion
of common resources for at least one UE among the plurality of UEs.
This can be performed using a known or pre-determined pattern to
likewise ensure necessary orthogonality. The process 500 then
terminates at end state 504.
[0166] After the mapping operation 530, an eNB sends the mapped
UE-RS PR sequences to a plurality of UEs in a cell. A particular UE
among the plurality of UEs can receive the PR sequences, extract a
UE-RS intended for the particular UE, and use the UE-RS for data
decoding purposes.
[0167] FIG. 6 is a flowchart illustrating an exemplary process 600
for receiving and using PR sequences of UE-RSs in MU-MIMO
configurations from a viewpoint of a user equipment (UE). The
process 600 begins at start state 601 and proceeds to operation 610
in which at least one PR sequence of a UE-RS is received by the UE
where the at least one PR sequence has been initialized independent
of a specific UE identifier and/or independent of a resource
bandwidth assigned to a specific UE.
[0168] The process 600 proceeds to operation 620 in which data is
received by the UE on a downlink (DL) bandwidth resource (e.g.,
PDSCH). The process 600 proceeds to operation 630 in which data
received on the downlink bandwidth resource is decoded by the UE
using the UE-RS. The process 600 terminates at end state 640.
[0169] In certain embodiments, as an extension of the embodiments
described above, it is possible to apply a group-based UE-RS
scrambling and PR sequence initialization. In such an embodiment,
UEs are assigned to different groups in a semi-static or in a
dynamic way and, within each group, a particular one of various
UE-independent UE-RS scrambling and sequence initialization
procedures described above can be applied.
[0170] In one aspect, a group index indicative of a particular
group to which a specific UE is assigned can be conveyed to the UE
through L3 or L2 layer signaling, for example. As an example, if
there are two groups, the group indices can be defined as 0 and 1.
A UE can be informed which group index, 0 or 1, the UE belongs to.
Group-based UE-RS sequence initialization allows for non-orthogonal
MU-MIMO UE-RS multiplexing when the total number of the layers for
co-scheduled UEs in MU-MIMO setup is beyond the number of UE-RS
orthogonal ports. For example, in the context of LTE Rel. 9, one
can consider two groups of scrambling sequences, say group A and
group B. It is possible to orthogonally multiplex 2 UEs of group A
(or group B), each receiving rank 1. In addition it is possible to
multiplex 2 UEs, each of rank 2, one from group A and one from
group B, or 4 UEs each of rank 1 transmission where 2 are from
group A and 2 are from group B.
[0171] Note that in this case the UEs can benefit from potential
optimization of MU interference estimation within the group that
the UE is semi-statically or dynamically assigned to. Also,
inter-group interference randomization can be realized this way.
Optimizations in designing the UE-RS scrambling for each group to
reduce the adverse impact across different groups can also be
employed.
[0172] In one aspect, an eNB can assign each UE to a particular one
of different groups based on one or more predetermined factors. For
example, an assignment of a particular UE to a particular group can
be based on a total number of currently active UEs in each group
and/or on one or more UE parameters or attributes of the particular
UE. For instance in a correlated antenna deployment, where the
channel directionality is changing slowly with time, UEs can be
grouped based on their dominant channel directions such that UEs in
different groups have dominant channel directions that are apart
from, or possibly orthogonal to, each other.
[0173] FIG. 7 is a block diagram depicting a system 700 that
facilitates generating UE-RSs and related resource mappings in an
MU-MIMO configuration. The system 700 includes an access point 702
that can be a base station, femtocell access point, picocell access
point, relay node, mobile base station, mobile device operating in
a peer-to-peer communications mode, and/or the like, for example,
that provides a wireless device 704 with access to a wireless
network. The wireless device 704 can be a user equipment (UE) such
as a mobile device, portion thereof, or substantially any user
equipment (UE) that can receive access to a wireless network.
[0174] The access point 702 can include a UE-RS sequence defining
component 706 that develops a plurality of reference signals that
can be used by one or more UEs to decode data over shared
resources, a UE-RS sequence initializing component 708 that creates
a pseudo-random sequence of the reference signals for the one or
more UEs, a UE-RS mapping component 710 that maps a UE to a given
pseudo-random sequence of UE-RSs, a device grouping component 703
that assigns UEs to which resources are assigned to one or more
groups, and an information signaling component 705 that
communicates the UE-RS mapping and/or grouping information to one
or more corresponding UEs. The wireless device 704 can include an
RS information receiving component 714 that obtains one or more
parameters related to RS transmissions from an access point and an
RS decoding component 716 that decodes one or more RSs based at
least in part on the parameters.
[0175] According to an example, as described above, RSs in an
MU-MIMO configuration can be CDM, FDM, and/or a combination
thereof. For example, where RSs are CDM, the access point 702 can
multiplex RSs according to pseudo random sequences selected for one
or more wireless devices. In an example, the UE-RS sequence
defining component 706 can generate a plurality of UE-RSs that can
be utilized to decode data sent over shared resources to one or
more UEs. In MU-MIMO configurations, it is to be appreciated that
devices having shared bandwidth assignments and/or location
assignments may not be completely aligned. Thus, UE-RS sequence
defining component 706 can generate the plurality of UE-RSs based
on an entire bandwidth of a related cell instead of based on PDSCH
bandwidth (as in LTE release 8). In another example (e.g., to
support multi-cell MU-MIMO), the UE-RS sequence defining component
706 can generate the UE-RSs in a bandwidth agnostic manner, such as
according to a maximum possible downlink bandwidth configuration in
terms of RBs.
[0176] Once the UE-RSs are defined, the UE-RS sequence initializing
component 708 can generate pseudo-random sequences of the UE-RS for
assigning to UEs to decode shared resources. In MU-MIMO
configurations, it can be desirable that antenna ports for wireless
devices paired to use the same PDSCH resources remain orthogonal.
To this end, the UE-RS sequence initializing component 708 can
initialize the UE-RS sequences based at least in part on a cell
identifier (as opposed to a UE identifier in LTE Rel-8). This can
ensure orthogonality since the antenna ports use the common metric.
In this regard, for example, other common metrics can be utilized,
such as resource block identifier, antenna port index, and/or the
like, that can be known for both antenna ports. The UE-RS mapping
component 710 can assign the pseudo-random sequences of UE-RS and
shared resources to one or more wireless devices using a
pre-determined mapping scheme that maintains the orthogonality
(e.g., sequentially from one end of the band, starting from the
center of the band, etc.).
[0177] The device grouping component 703 can assign wireless device
(UE) 704 to one or more groups (e.g., randomly, or based on a
number of active UEs in a group, parameters of the device, and/or
the like, as discussed above). In this regard, UE-RS sequence
initializing component 708 can initialize the UE-RS sequences for
the wireless device 704 based on the assigned group. Using
group-based sequence initialization, in one example, can ensure
orthogonality among devices depending on a received rank. For
example, if there are two UE-RS ports, where the device grouping
component 703 assigns the wireless device 704 to a group and the
wireless device 704 receives rank 1, the UE-RS sequence
initializing component 708 can initialize orthogonal sequences for
the wireless device 704 and another device in the same group
receiving rank 1. Similarly, where the device grouping component
703 assigns the wireless device 704 to a group and the wireless
device 704 receives rank 2, the UE-RS sequence initializing
component 708 can initialize orthogonal sequences for the wireless
device 704 and another device in a separate group receiving rank
2.
[0178] The information signaling component 705 can signal
pseudo-random sequences, related resources, and/or related
parameters corresponding to the wireless device 704. At wireless
device (UE) 704, the RS information receiving component 714 can
obtain the pseudo-random sequences, related shared resources,
and/or parameters from the access point 702. The RS decoding
component 716 can decode RSs specific to the wireless device 704
from the access point 702 over the shared resources using the
pseudo-random sequences, for example. Similarly, in one example,
the information signaling component 404 of access point 702 can
transmit grouping information to the wireless device 704 (e.g.,
using L3 layer signaling).
[0179] FIG. 8 is a flowchart illustrating an exemplary process 800
for assigning and initializing sequences of UE-RSs in MU-MIMO
configurations from a viewpoint of an access point (e.g., eNB). The
process 800 begins at start state 801 and proceeds to operation 810
in which a plurality of UEs are assigned to different UE groups
based on one or more predetermined factors. As described above, the
predetermined factors can include, but are not limited to, a total
number of currently active UEs in each UE group, dominant channel
directions of UEs and/or locations of UEs within a cell.
[0180] The process 800 proceeds to operation 820 in which
pseudo-random (PR) sequences of UE-RSs for use by a plurality of
UEs are initialized based on the assigned UE groups. In particular,
the initialization of each PR sequence associated with each UE-RS
for a particular UE can be based on a group ID indicative of the UE
group to which the particular UE has been assigned. By way of
example, in the initializing operation 820, c.sub.init is an
initial value of a pseudo-random sequence generator associated with
each UE-RS and is a function defined by
c.sub.init=f(N.sub.ID.sup.cell,.left brkt-bot.n.sub.s/2.right
brkt-bot., n_groupID) wherein:
[0181] N.sub.ID.sup.cell is a cell ID,
[0182] n.sub.s is a slot number, and
[0183] n_groupID is a group ID.
[0184] Furthermore, in some embodiments, in the initializing
operation 820, the initialization of each PR sequence associated
with each UE-RS is independent of a specific UE identifier and/or
independent of a resource bandwidth assigned to a specific UE. As
discussed above, the first independence relating to the UE-RS PR
sequence initialization can be achieved by removing the UE
identifier from the initialization such as the one defined by
equation (3) above; and/or by making the initialization a function
of non-UE specific attributes such as RB.sub.ID, AntPortIdx,
RB.sub.ID, N.sub.CP, or any combinations thereof. The second
independence relating to the resource bandwidth can be achieved by
initializing a plurality of UE-RSs based at least in part on a
bandwidth of a specific cell that includes the plurality of UE-RSs.
As described above, this removes dependency on the resource
bandwidth associated with the particular UE, which mitigates the
need for related UEs to be aligned when receiving UE-RS sequences
and related resource assignments.
[0185] The process 800 proceeds to operation 830 in which PR
sequences of the UE-RSs are generated using a procedure defined by
equation (1), for example. The PR sequences can be generated using
common (non-UE specific) identifiers, such as a cell identifier
(N.sub.ID.sup.cell), a resource block identifier (RB.sub.ID), a
group ID (n_groupID), etc., so cell antennas can retain
orthogonality of sequence assignment for devices having similar
assigned resources.
[0186] The process 800 proceeds to operation 840 in which at least
one of the UE-RS PR sequences thus generated is mapped to a portion
of common resources for at least one UE among the plurality of UEs.
This can be performed using a known or pre-determined pattern to
likewise ensure necessary orthogonality. The process 800 terminates
at end state 850.
[0187] FIG. 9 is a flowchart illustrating an exemplary process 900
for receiving and using sequences of UE-RSs in MU-MIMO
configurations from a viewpoint of a user equipment (UE). The
process 900 begins at start state 901 and proceeds to operation 910
in which at least one PR sequence of a UE-RS is received by a UE
where the at least one PR sequence has been initialized based on a
group index indicative of a UE group to which the UE belongs.
Furthermore, in certain embodiments, the PR sequence has been
initialized independent of a specific UE identifier and/or
independent of a resource bandwidth (PDSCH) assigned to a specific
UE.
[0188] The process 900 proceeds to operation 920 in which data is
received by the UE on a downlink (DL) bandwidth resource (e.g.,
PDSCH). The process 900 proceeds to operation 930 in which data
received by the UE on the downlink bandwidth resource is decoded by
the UE using the received UE-RS. The process 900 terminates at end
state 940.
[0189] Those of skill would further appreciate that the various
illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the aspects disclosed herein may be
implemented as electronic hardware, computer software, or
combinations of both. To clearly illustrate this interchangeability
of hardware and software, various illustrative components, blocks,
modules, circuits, and steps have been described above generally in
terms of their functionality. Whether such functionality is
implemented as hardware or software depends upon the particular
application and design constraints imposed on the overall system.
Skilled artisans may implement the described functionality in
varying ways for each particular application, but such
implementation decisions should not be interpreted as causing a
departure from the scope of the present disclosure.
[0190] As used in this application, the terms "component",
"module", "system", and the like are intended to refer to a
computer-related entity, either hardware, a combination of hardware
and software, software, or software in execution. For example, a
component may be, but is not limited to being, a process running on
a processor, a processor, an object, an executable, a thread of
execution, a program, and/or a computer. By way of illustration,
both an application running on a server and the server can be a
component. One or more components may reside within a process
and/or thread of execution and a component may be localized on one
computer and/or distributed between two or more computers.
[0191] The word "exemplary" is used herein to mean serving as an
example, instance, or illustration. Any aspect or design described
herein as "exemplary" is not necessarily to be construed as
preferred or advantageous over other aspects or designs.
[0192] Various aspects will be presented in terms of systems that
may include a number of components, modules, and the like. It is to
be understood and appreciated that the various systems may include
additional components, modules, etc. and/or may not include all of
the components, modules, etc. discussed in connection with the
figures. A combination of these approaches may also be used. The
various aspects disclosed herein can be performed on electrical
devices including devices that utilize touch screen display
technologies and/or mouse-and-keyboard type interfaces. Examples of
such devices include computers (desktop and mobile), smart phones,
personal digital assistants (PDAs), and other electronic devices
both wired and wireless.
[0193] In addition, the various illustrative logical blocks,
modules, and circuits described in connection with the aspects
disclosed herein may be implemented or performed with a general
purpose processor, a digital signal processor (DSP), an application
specific integrated circuit (ASIC), a field programmable gate array
(FPGA) or other programmable logic device, discrete gate or
transistor logic, discrete hardware components, or any combination
thereof designed to perform the functions described herein. A
general purpose processor may be a microprocessor, but in the
alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also
be implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0194] Furthermore, the one or more versions may be implemented as
a method, apparatus, or article of manufacture using standard
programming and/or engineering techniques to produce software,
firmware, hardware, or any combination thereof to control a
computer to implement the disclosed aspects. The term "article of
manufacture" (or alternatively, "computer program product") as used
herein is intended to encompass a computer program accessible from
any computer-readable device, carrier, or media. For example,
computer readable media can include but are not limited to magnetic
storage devices (e.g., hard disk, floppy disk, magnetic strips . .
. ), optical disks (e.g., compact disk (CD), digital versatile disk
(DVD) . . . ), smart cards, and flash memory devices (e.g., card,
stick). Additionally it should be appreciated that a carrier wave
can be employed to carry computer-readable electronic data such as
those used in transmitting and receiving electronic mail or in
accessing a network such as the Internet or a local area network
(LAN). Of course, those skilled in the art will recognize many
modifications may be made to this configuration without departing
from the scope of the disclosed aspects.
[0195] The steps of a method or algorithm described in connection
with the aspects disclosed herein may be embodied directly in
hardware, in a software module executed by a processor, or in a
combination of the two. A software module may reside in RAM memory,
flash memory, ROM memory, EPROM memory, EEPROM memory, registers,
hard disk, a removable disk, a CD-ROM, or any other form of storage
medium known in the art. An exemplary storage medium is coupled to
the processor such the processor can read information from, and
write information to, the storage medium. In the alternative, the
storage medium may be integral to the processor. The processor and
the storage medium may reside in an ASIC. The ASIC may reside in a
user terminal. In the alternative, the processor and the storage
medium may reside as discrete components in a user terminal.
[0196] In one or more exemplary embodiments, the functions
described may be implemented in hardware, software, firmware, or
any combination thereof. If implemented in software, the functions
may be stored on or encoded as one or more instructions or code on
a non-transitory computer-readable medium. Computer-readable media
includes computer storage media. Storage media may be any available
media that can be accessed by a computer. By way of example, and
not limitation, such computer-readable media can comprise RAM, ROM,
EEPROM, CD-ROM or other optical disk storage, magnetic disk storage
or other magnetic storage devices, or any other medium that can be
used to carry or store desired program code in the form of
instructions or data structures and that can be accessed by a
computer. Disk and disc, as used herein, includes compact disc
(CD), laser disc, optical disc, digital versatile disc (DVD),
floppy disk and blu-ray disc where disks usually reproduce data
magnetically, while discs reproduce data optically with lasers.
Combinations of the above should also be included within the scope
of non-transitory computer-readable media.
[0197] The previous description of the disclosed aspects is
provided to enable any person skilled in the art to make or use the
present disclosure. Various modifications to these aspects will be
readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other embodiments
without departing from the spirit or scope of the disclosure. Thus,
the present disclosure is not intended to be limited to the
embodiments shown herein but is to be accorded the widest scope
consistent with the principles and novel features disclosed
herein.
[0198] In view of the exemplary systems described supra,
methodologies that may be implemented in accordance with the
disclosed subject matter have been described with reference to
several flow diagrams. While for purposes of simplicity of
explanation, the methodologies are shown and described as a series
of blocks, it is to be understood and appreciated that the claimed
subject matter is not limited by the order of the blocks, as some
blocks may occur in different orders and/or concurrently with other
blocks from what is depicted and described herein. Moreover, not
all illustrated blocks may be required to implement the
methodologies described herein. Additionally, it should be further
appreciated that the methodologies disclosed herein are capable of
being stored on an article of manufacture to facilitate
transporting and transferring such methodologies to computers. The
term article of manufacture, as used herein, is intended to
encompass a computer program accessible from any computer-readable
device, carrier, or media.
[0199] It should be appreciated that any patent, publication, or
other disclosure material, in whole or in part, that is said to be
incorporated by reference herein is incorporated herein only to the
extent that the incorporated material does not conflict with
existing definitions, statements, or other disclosure material set
forth in this disclosure. As such, and to the extent necessary, the
disclosure as explicitly set forth herein supersedes any
conflicting material incorporated herein by reference. Any
material, or portion thereof, that is said to be incorporated by
reference herein, but which conflicts with existing definitions,
statements, or other disclosure material set forth herein, will
only be incorporated to the extent that no conflict arises between
that incorporated material and the existing disclosure
material.
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